Now I have a transmission noise - diagnosis help please.

[mikerophone]

Got my engine noise sorted, hooked up the driveshaft and now I have a transmission noise...

It seems to get louder as I up shift. Here's the history - I bought an 82 850L with 12k on it to be a donor for my ~42k 81 850G. I only rode it a few times once I degummed the tank and carbs since it sat for 23 years and it ran fine up to 3rd gear in my neighborhood. Without being licensed I didn't want to take it outside my neighborhood. PO lost interest in 92 and parked it I'm told. I removed the motor, soda and glass bead blasted it, painted it and swapped it into my G. My tape job for the masking around the clutch cover and stator cover wasn't perfect and I did get a little bit of glass bead inside the crankcase so I ran the engine for a few minutes with fresh oil in it and drained it. My engine noise thread is here.

One thing I did that I shouldn't have when I had the oil drained after painting was turn the motor over several times while I checked the valve clearance before ordering my shims from Ray and the shim club. I thought the noise might be from slop in the final drive or bad splines so I swapped over the whole final drive setup and wheel from the L but sadly the noise is in still the transmission area. I drained and changed the oil just in case and there was about a quarter's size pile of glass beads in the oil filter cavity. Oil pump strained perhaps? The oil pressure light goes off as soon as I start it but I noticed that there's none in the sight glass after filling and starting it...

I also should pull the boot back and verify all 4 output shaft to driveshaft bolts are tight, I did use locktite on them so I doubt that's it but I'm putting it out there for the experts.


Here's the YouTube video of the transmission noise:

[mikerophone]

I haven't ridden it yet, just had it on the center stand, and I never thought to run the donor bike through the gears on the stand, it went fine down the road here in my neighborhood.

From another thread, it would be great if this was all it is:

My bike does the same thing if I run it through gears on the centre stand
bike needs a load and the tire is not much of a load.

I also read that the clutch hub nut can make a similar noise, but I didn't touch it. Can pull the cover and check tonight I suppose. I did pull the cover the other night and make sure there was no blasting media in there. Should I pull the oil pump gears?

Hoping for some direction from someone who has had this issue before if possible. I know nothing about transmissions...

[uk gs nut]

Could be bevel drive gears bust a tooth

[mikerophone]

I sure hope not! Anyone else have a diagnosis?

Can rotating the engine without oil in it several times by hand bust a tooth off the bevel drive gears?

[Brendan W]

Can rotating the engine without oil in it several times by hand bust a tooth off the bevel drive gears?

That would be a first imho. The noise sounds more wheel related than any of the faster spinning stuff.

[mikerophone]

I do hope so, I'm going to drain and change the gear oil again tonight and perhaps take it for a short spin in the hopes that the weight of me and straightening out the driveshaft a bit has something to do with it. Perhaps the driveshaft splines aren't all the way seated in the final drive... Doubt it though.

[mikerophone]

Well it's not the gear oil, it was maybe a tablespoon low but the sound is definitely in the driveshaft/swing arm area. What a relief. It makes a slight dragging/scraping noise with the bike on the winter stand in neutral while spinning the rear wheel. I'm a little hesitant to take it for a spin until I pull the swing arm and have a look however.

I did use the new driveshaft and everything else from the donor bike except the swing arm since they are different between the G and the L - shock mount on the right side has a bracket instead of a bolt on the L. I suppose I could throw the old shaft back in but I lined them up next to each other before I switched them and they sure seemed the same. No way to internally grease the U joints on them like a trucks shaft either but they both weren't extremely stiff nor had play in them.